The patterns produced in the cloth generated by Automatic Warp Knitting Machines and/or Crochet Warp Knitting Machines are dependent on the movement of pattern bars. In all instances, the pattern bars rest at one end against a cam or a cam-like device. Contact is maintained against the cam or cam-like device or push rod by the use of spring tension to maintain the mechanical interfacial contact between the pattern bars and the push rod or cam or cam-like device. The contours of the cam or cam-like device constitute the encoding means by which the reciprocal motion of the pattern bars is controlled to generate the desired pattern in the cloth. In some instances, a computer or computer-like device has been substituted for the cam or cam-like device, but even in those instances, the return cycle of the reciprocating pattern bar is determined by spring loaded tensions. Therefore, in all cases, the force required to move the pattern bars is increased by the force required to tension the spring. Conversely, the spring tension increases the frictional force required to move the cams or cam-like devices on the return stroke of the reciprocal motion of the pattern bars. Some Automatic Warp Knitting/Crochet Warp Knitting Machines have substituted computer controlled stepping motors to activate the push rods instead of the cams or cam-like devices. However, this type of machine still operates against spring tension as stated above throughout the entire reciprocal stroke of the pattern bars. In all such machines, the pattern bars must be of substantial mass in order to be stable against the friction caused by the spring loaded tension.
The cams, or cam-like devices, are the encoding means by which the knitting machine is programmed to produce a specific cloth pattern. The cam-like devices are chains which are driven by a sprocket-type drive, to which shapes are attached. These shapes act as cams and through the medium of the push rods and springs cause the pattern bars to follow a prescribed reciprocal motion on a repetitive program in direct mechanical synchronism with all the other associated mechanical parts, such as the needles, yarn guide tubes, yarn guide tube lifting bars and the machine's main shaft. The cams perform exactly the same function as the cam-like devices except the pattern is in the form of one integrated shape instead of a plurality of shapes attached to a chain and sprocket drive. Whether the encoding is accomplished through the use of a cam, or a cam-like device, the actual encoding takes a large number of manhours to accomplish. Where the reciprocal motion of the pattern bars is controlled by a programmed computer, the ubiquitous spring tension requires heavier members, higher torque and therefore, higher moment of inertia, all of which complicate the control problems for the pattern bars and also increase machine vibration and machine wear.
The ball screw/ball nut arrangement which is rotably attached to the shaft of the stepping motors in such a manner as to convert the rotational movement of the motor drive shaft into the reciprocating motion of the push rods also have to be of considerable mass. The mass requirements are necessary since there is always load on the system from the spring loading of the pattern bars. The constant spring tension causes a varible load to exert on the pattern bars in that as the pattern bars are driven away from the cam end of the machine, the drive mechanism must not only work against the mass of the pattern bar assembly, but, also against the tension of the springs which load increases according to the stress applied according to Hooke's Law. Therefore, the highest ratio of mechanical loadings occur when the push rods are pushing against the pattern bars and the springs. The lowest ratio of mechanical loadings occur when the cams or cam-like devices allow the push rods to retreat from their extended position down the relief side of the cam.
The differences in the mechanical loading affect the system insofar as the rate of extension of the pattern bars is compared to the rate of retreat down the relaxed side of the cam. This leads to a different rate of extension versus the rate of retreat. Since the rest of the machine is still operating at a standard speed and the pattern bars move perpendicularly to the warp threads of the machine, an anisotropic pattern must be and is produced in the cloth, at all times, as an uncontrolled function.
The present invention, when running at a constant speed, produces a completely uniform cloth. There is no anisotropy present. The rate of the extension stroke is substantially the same as the rate for the retreating stroke. The new machine runs quietly without vibration and its attendant wears. The new machine can function well with lower torque drive motors with lower moments of inertia. The mass of the pattern bar assemblies can be lighter than on the conventional machine. This machine eliminates the need for a spring loaded return or retreat cycle; eliminates the spring loaded interface between the push rods and the pattern bars; and eliminates an element of the machine known as the guide tube lifting bar. This element is present in other machines to remove the tubes which guide the yarn to the needles which knit the cloth and its purpose is to prevent the knitting needles, guide tubes and yarn from getting entangled when the machine indexes to the location for the next series of knitting stitches required by the pattern being produced by the machine. The elimination of the return springs, cams or cam-like devices, push rods, guide tube lifting bars and vibration all allow the new machine to operate at a greater number of cycles per unit time. The elimination of vibration together with the more precise control of the action and position of all the active members of the new machine has increased the range of versatility and utility of the machine since this machine can utilize knubbly yarns such as boucles, or novelty yarns such as sequin strings.